This invention relates to an ultrasonic ranging device, and more particularly to an improved ultrasonic ranging device having a casing body and a control means specifically designed for being automatically operated to protect the ranging device against water, dust and mud so as to promote the ranging efficiency and prolong the life expectancy of the ranging device.
It is known that some vehicles are equipped with an ultrasonic ranging device attached at a rear side of the vehicle trunk for being used to detect the distance between the rear bumper of the vehicle and an object therebehind when the vehicle is geared to reverse so as to prevent the vehicle from bumping against the object. However, because the known ultrasonic ranging devices installed on the back end of vehicles are constantly exposed to the elements, the outer surface thereof soon becomes covered with foreign materials such as dust, mud, etc. Consequently, not only is the detecting function of the ranging device affected, the life expectancy is also shortened.